There are known in the art multi-station time molding machine the linear or rotary type, in which one plasticating screw barrel feeds two or more injection molds.
The drawback of the linear-type machines is the necessity for each station to be provided with a clamping device, which is one of the most heavy and complex units of the machine. The rotary-type machines comprise a complex and heavy unit, also, i.e. a rotating dividing table and, in addition, they are not adapted for molding large-sized parts.
There are further known two-station machines with one screw barrel and clamping unit, but they have the substantial drawback, in that the screw barrel is movable and follows the motion of the opening mold halves, while the individual opening of the molds requires a hydraulic device, which operates with a complex hydraulic system comprising several pressure steps.
A basic drawback of all molding machines for the processing of slowly solidifying materials is that the whole machine is standing idle until the material injected into the mold cools and solidifyies. This drawback is particularly striking in the production of structural foam parts, which are usually thick-walled. Their heat-conductivity is impaired because of their cellular core structure and the heat-retaining gas inside the cells, the mold having to remain closed until the formation of a compact skin of sufficient rigidity to allow the part to be removed without a deformation thereof.